This invention relates to the stabilization of molded parts, by fixing their dimensions and external configurations, and more particularly, to the high speed stabilization of such parts to enhance production capacity.
In the production of molded parts, molten material is forced into the cavity of a mold through openings called sprues and channels called runners. When the mold is opened, the desired or production product is expelled, along with a by-product formed in the sprue and runner channels. The latter is waste material which must be segregated from the production parts. This can be done manually but that is time consuming and inefficient.
Since the parts, both production and by-product, are produced from molten material, they initially are in an elevated temperature condition.
If the parts are expelled immediately, their dimensions and configurations can change significantly during cooling. When attempts are made to accelerate the cooling, the result often is shrinkage of the parts and loss of dimensional stability. In one attempt to achieve dimensional stability, i.e. reduce the changes that take place in the dimensions of the molded parts during cooling, the parts are allowed to cool partially in the mold before being expelled. The presence of the mold helps constrain the parts during cooling, but this procedure has the disadvantage that the increased residence time of the parts in the mold can seriously reduce the speed with which the parts are produced. In addition, since the parts are not completely cooled before expulsion, they are still subject to dimensional and configuration changes during subsequent cooling.
Even where dimensional and configurational stability are not significant considerations, prompt expulsion of parts from the mold requires that they be allowed to cool on an appropriate surface before they are subjected to further processing. This interferes with the molding operation and the rapid and efficient production of parts. There is either a production delay or a long conveyor must be used so that the parts will cool sufficiently before the next step in processing. Another technique has been to use a short conveyor with cooling fans but this technique has proved inadequate because it has been incapable of imparting sufficiently uniform cooling to the expelled parts.
Moreover, some molded materials require not only stabilization, but also conditioning. An example is nylon which can be too brittle for further processing unless its moisture content is at the right level.
Accordingly, it is an object of the invention to facilitate the production of molded parts. A related object is to facilitate the conditioning and stabilization of molded parts, particularly at high production rates. Another related object is to facilitate the handling of parts expelled from a mold in a relatively uniform and consistent manner.
Another object of the invention is to facilitate the cooling of molded parts, particularly at high production rates. A related object is to eliminate the shrinkage of parts and the need for in-mold cooling and its attendant reduction in the number of useful parts that can be produced in a given period of time. Another related object is to stabilize molded parts beyond the level attainable with in-mold cooling.
A further object of the invention is to eliminate the use of long conveyors in attempting to achieve high-speed stabilization of molded parts. A related object is to achieve stabilization beyond that achievable using long cooling conveyors.
A still further object of the invention is to eliminate the use of cooling fans with conveyors in attempting to achieve high-speed stabilization of molded parts. A related object is to achieve stabilization beyond that achievable with fan cooled conveyors.
Still another object of the invention is to achieve suitable segregation of production and by-product parts in a relatively rapid molding cycle. A related object is to permit the handling of parts expelled from a mold at a high mold operation rate.